rgwlc: fix error return from backward-compat decode

Exception handling in backward-compat case returned EIO even when
the actual backward-compat decode succeeded.

Fixes: https://tracker.ceph.com/issues/46677

Signed-off-by: Matt Benjamin <mbenjamin@redhat.com>

src/cls/rgw/cls_rgw.cc

@@ -3775,13 +3775,14 @@ static int rgw_cls_lc_list_entries(cls_method_context_t hctx, bufferlist *in,
       /* try backward compat */
       pair<string, int> oe;
       try {
-	decode(oe, iter);
+	iter = it->second.begin();
+	::decode(oe, iter);
 	entry = {oe.first, 0 /* start */, uint32_t(oe.second)};
       } catch(buffer::error& err) {
 	CLS_LOG(
 	  1, "ERROR: rgw_cls_lc_list_entries(): failed to decode entry\n");
+	return -EIO;
       }
-      return -EIO;
     }
    op_ret.entries.push_back(entry);
   }